Effects of Diabatic Cooling in a Shear Flow with a Critical Level

Publisher Website
Google Scholar
Abstract
The response of a two-dimensional, stably stratified shear flow to diabatic cooling, which represents the evaporative cooling of falling precipitation in the subcloud layer, is examined using both a linear analytical theory and a nonlinear numerical model. The ambient wind is allowed to reverse its direction at a certain height and the cooling is specified from the surface to a height below the wind reversal level. From a scale analysis of the governing equations a nonlinearity factor of the thermally induced finite-amplitude wave, gQ0l(cpT0U02N), is found. From a scale analysis of the linear system, it is shown that the wind shear can modify the condition in which the upstream propagation of the density current is opposed by the ambient wind. When the shear and the basic wind are of opposite sign, small basic wind is enough to prevent the upstream propagation of the density current. This is because part of the cooling is used to compensate the positive vorticity associated with the positive wind... Abstract The response of a two-dimensional, stably stratified shear flow to diabatic cooling, which represents the evaporative cooling of falling precipitation in the subcloud layer, is examined using both a linear analytical theory and a nonlinear numerical model. The ambient wind is allowed to reverse its direction at a certain height and the cooling is specified from the surface to a height below the wind reversal level. From a scale analysis of the governing equations a nonlinearity factor of the thermally induced finite-amplitude wave, gQ0l(cpT0U02N), is found. From a scale analysis of the linear system, it is shown that the wind shear can modify the condition in which the upstream propagation of the density current is opposed by the ambient wind. When the shear and the basic wind are of opposite sign, small basic wind is enough to prevent the upstream propagation of the density current. This is because part of the cooling is used to compensate the positive vorticity associated with the positive wind...
Keywords

This publication has 0 references indexed in Scilit: